Meeze, I own one of the Toyota Sludge Monsters. It's a 1998 Toyota Sienna van with the 3.0 V-6. Motor started sludging at 30,000 miles in spite of 3,000 mile oil changes. Was using dino oil, 5w-30 Havoline with occasional Pennzoil. Toyota Service Mgr. suggested I switch to Mobil 1 5w-30 with 5,000 OIC. I did this and the sludge slowly dissapated and have not had any sludging problem since and I now have 74,000 miles on the van. This motor tends to run hot and the synthetic seems to not break down and sludge-up the way conventional oil did. This is just my own personal experience and I'm not trying to start a synthetic versus dino war.